Western Sydney's roads a NSW budget focus

The NSW government is saving the best for the west in Tuesday's budget, estimating the population of western Sydney will boom from two million to three million people over the next 20 years.

The NSW budget 2019-20 secured more than $1 billion in funding for critical road projects across the region, Transport Minister Andrew Constance told reporters on Sunday.

This includes $107.4 million invested on the M4 Smart Motorway between Parramatta and Penrith.

Government figures show more than 845,000 journeys to work start and end in western Sydney, with almost two thirds of those being by car.

Mr Constance also announced the M4 tunnels within WestConnex will open in the next four to eight weeks, allowing road users to skip 22 sets of traffic lights along Parramatta Road between Haberfield and Homebush.

But, he acknowledged the controversial WestConnex project - which is "incomplete" and due to finish by 2023 - had required the acquisition of some residential properties.

"You can't build mega projects in this city without construction disruption and we want to thank the community for their patience," Mr Constance said.

"We must recognise, obviously, the difficulties for those whose homes were acquired for the benefit of the greater community, in terms of our city ... but that pain is now behind us."

There will be no toll free period for the new M4 tunnels, the transport minister's office has confirmed.

Treasurer Dominic Perrottet said the budget will help to deliver more than 40 road projects across western Sydney but will also create jobs, estimating 2000 people are currently involved and expecting this figure to rise.